1. Field of the Invention
The present invention relates to a seat slide device for a vehicle, etc., which comprises a lower rail and an upper rail.
2. Description of the Related Art
Heretofore, a seat slide device for a vehicle, etc., which comprise a lower rail and an upper rail, has been widely known. This type of seat slide device is disclosed, for example, in JP 2002-225608A. As illustrated in FIG. 14A, a seat slide device 300 disclosed in JP 2002-225608A comprises a lower rail 301 and an upper rail 302. The lower rail 301 has a bottom wall 301a, a pair of sidewalls 301b, and a pair of bended pieces 301c extending inwardly from respective upper edges of the sidewalls 301b to define an upper opening 301d. 
Then, as illustrated in FIG. 14B, the lower rail 301 is mounted on a floor of a vehicle body in such a manner that each of longitudinally opposite ends of the lower rail 301 is fixed to a leg 303 fixed to the floor of the vehicle body, by using a bolt 304 inserted in the lower rail 301 through the upper opening 301d to serve as a fixing member. Further, a sliding piece 302a provided on an upper rail 302 is inserted in a sliding groove 301e defined between associated ones of the sidewalls 301b and the bended pieces 301c, through an interspace 305 defined between the bottom wall 301a and each of the bended pieces 301c of the lower rail 301, to allow the upper rail 302 to be slidingly moved along the longitudinal direction of the lower rail 301.
However, in the seat slide device 300 disclosed in JP 2002-225608A, a head 304a of the bolt 304 is disposed to protrude upwardly from an upper surface of the bottom wall 301a of the lower rail 301 by a length equal to a thickness of the head 304a. Thus, for example, if a foreign object 10, such as a candy or a toy block, intrudes in the lower rail 301 through the upper opening 301d, when the upper rail 302 is slidingly moved along the lower rail 301, the foreign object 10 is likely to be pinched between the head 304a of the bolt 304 and an end face 302b of the upper rail 302 and broken into pieces.
Otherwise, the foreign object 10 intruding into the lower rail 301 is likely to enter the sliding groove 301e through the interspace 305. This is liable to preclude smooth sliding movement of the upper rail 302.
It is an object of the present invention to provide a seat slide device capable of, even if a foreign object intrudes in a lower rail, allowing the foreign object to become less likely to be broken into pieces, or allowing the foreign object to become less likely to hinder smooth sliding movement of an upper rail.